In the field of the cloth printing, an ink-jet print method is demanded for responding to shortening of delivery period and producing of various kind products in small amount. Disperse dyes are usually employed for dying of the fiber such as polyester fiber. When the disperse dye is employed for ink-jet printing, however, there are many restrictions on the selection of the dye such as the dispersion suitability for making fine particles, prevention of nozzle blocking and stability of the dispersion, additionally to the usual standard of selection of the dye such as the tone and fastness since the dye is ejected from a fine nozzle. Moreover, there are subjects such as prevention of blocking of the fine nozzle by coarse particles and the variation of the physical properties of the ink and the precipitation of solid components in the course of the production and storage of the ink. In the ink in which the disperse dye is employed as the colorant, the coarse particles are easily formed compared with a dye ink which is a complete solution because the large particles contained in the disperse dye ink include large particles formed by the aggregation of the dispersed colorant particles during the storage additionally to a fine dust particles since such the ink is a dispersion system comprising the colorant particles dispersed in an aqueous medium. Japanese Patent Publication Open to Public Inspection, hereinafter referred to as Japanese Patent O.P.I. Publication, No. 64-48875 described a method to remove the coarse particles in the ink causing the blocking of the nozzle and the precipitation of the solid components by filtration or centrifuge in the course of the production process.
Moreover, various proposes to stably disperse the pigment in the ink composition have been presented. For example, Japanese Patent Examined Publication No. 55-35434 proposes the application of a polymer having a lipophilic portion and a hydrophilic portion as the dispersing agent for dispersing the pigment. Japanese Patent Examine Publication No. 4-5703 proposes the employment of a polymer having a lipophilic portion having a molecular weight within a specified range and a hydrophilic portion as the dispersing agent for dispersing the pigment.
In the disperse dye ink, sufficient stability cannot be obtained by the method of removing the coarse particles in the course of the production, and the problems cannot completely solved by optimization of the kind of the surfactant or the dispersing agent by the same approach in the case of pigment.
On the other hand, gas dissolved in the ink some times causes degradation of the resolution and the clarity of the printed image, and formation of fine bubbles causing the blocking of nozzle. Japanese Patent O.P.I. Publication No. 10-298470 describes a method to remove by permeation of the dissolved gas by passing the ink through a hollow fiber membrane having gas permeability and reducing the pressure outside of the hollow fiber membrane. Such the method, however, does not bring sufficient effect on the entire inks, and the bubbles in the disperse dye ink are difficultly removed by such the deaeration treatment.
In the above situation, the object of the invention is to provide an ink-jet cloth printing ink excellent in the jetting ability and the storage stability.